1. Field of the Invention
The present invention relates to an optical pickup, and more particularly, it relates to a high-performance and low-priced optical pickup, employed for a disk player such as a DVD, for example, causing no reading error.
2. Description of the Background Art
For example, Japanese Patent Laying-Open No. 8-7321 describes an optical pickup. FIG. 8 is a schematic sectional view showing an example of such a conventional optical pickup. Referring to FIG. 8, a photodiode PD is arranged in an opening 3a formed on an end of a light transmission hole 3 provided with a half mirror 2 in a pickup body 1, while a collimator lens CL and an objective lens OL are arranged in another opening 3b formed on another end of the light transmission hole 3. A laser diode LD is stored in a branch hole 4 formed on a side surface of the pickup body 1. A printed board 6 connected with the photodiode PD and the laser diode LD through flexible cables 5 is fixed to the outer peripheral surface of the pickup body 1 with a machine screw 7.
A support substrate 8 supports the laser diode LD. A plug-in unit 10 is connected to a connector 9 fixed to the printed board 6 thereby connecting the photodiode PD and the laser diode LD to a control part (not shown) such as a microcomputer.
In the optical pickup shown in FIG. 8, the laser diode LD projects a laser beam onto a disk D through the half mirror 2, the collimator lens CL and the objective lens OL and the photodiode PD receives the laser beam reflected by the disk D through the half mirror 2 thereby reading information recorded in the disk D.
In this case, however, the laser diode LD disadvantageously generates heat due to the projection of the laser beam, and is reduced in capacity. In general, therefore, the pickup body 1 is molded by die-cast aluminum for prompting heat dissipation, while such a pickup body 1 of die-cast aluminum is high-priced.
Therefore, the pickup body 1 may be molded by low-priced hard synthetic resin while forming the support substrate 8 for the laser diode LD by a metal plate thereby prompting heat dissipation.
In the aforementioned structure, the metal support substrate 8 for the laser diode LD prompts heat dissipation. When the size of the support substrate 8 is increased for improving the heat dissipation effect, however, the bulked support substrate 8 comes into contact with a peripheral device. Therefore, the support substrate 8 is limited in size. When a high-performance laser diode LD is employed, further, the pickup body 1 is thermally expanded and deformed as shown by a phantom line in FIG. 8 due to high calorific power of the laser diode LD, and an optical axis O connecting the photodiode PD and the objective lens OL may be bent to cause a reading error. Therefore, the laser diode LD must be formed by that having low calorific power, disadvantageously leading to a narrow selection range for the laser diode LD.